Solenoid-operated valves are used in a variety of applications, generally to control the flow of fluid, and can be configured to be in a normally-closed or normally-open position when the solenoid is de-energized and in the opposite position when the solenoid is energized. In some applications, solenoid-operated valves are utilized in automobiles in thermal management systems for transmission fluid or engine coolant.
In some thermal management systems, for example transmission fluid or engine coolant, the default, or de-energized, solenoid-operated valve position directs the coolant flow from the engine or transmission to a cooler. Under certain circumstances, for example cold weather starting and initial operation of the automobile, it may be beneficial to bypass the cooler and return the coolant to the engine or transmission to shorten the warm-up period necessary for the fluid to reach optimal operating temperature. Typically this requires the solenoid to remain in the energized state for extended periods of time.
Current solenoids, if adapted for use in some thermal management systems, would require the solenoid to remain in the energized state until operating temperature of the controlled fluid was reached. Maintaining the solenoid in the energized condition can cause the activating coil to undesirably heat up, leading to increased resistance and the associated decrease in current. At a decreased current, the coil may produce a reduced magnetic field causing the solenoid to return to a default position, and thereby prematurely directing the fluid flow to the cooler.
In some cases, for example in energy sensitive applications, it may be impossible, undesirable, or impractical to provide the necessary power to maintain a solenoid-operated valve in the energized state for the required period of time.
Accordingly, the need exists for a solenoid operated valve that overcomes the above noted deficiencies.